Titanate materials offer useful electrical, optical, and mechanical properties. One use for titanate is in forming thermal sensors in thermal imaging systems to detect infrared radiation and to produce an image capable of being visualized by the human eye. These thermal sensors are generally formed by defining a plurality of sensors in bulk titanate by an etching process.
Previously developed methods for etching titanate substrates have generally involved isotropic wet chemical processes. Wet etching processes may suffer from several disadvantages. Wet chemical processes may etch isotopically in all directions and can lead to undercutting of masking material. This can limit the dimensions achievable through wet etching to relatively large structures. Wet chemical etching a titanate substrate can also contaminate the titanate. Additionally, wet chemical etching processes do not always integrate well into large quantity production lines and may result in liquid waste streams that require expensive disposal procedures and techniques.
Dry or anisotropic etching processes for titanate substrates have also been previously developed. These dry etching processes typically require extreme conditions of either temperature, laser light, or ion bombardment. These dry etching processes generally rely on high temperature or chemical approaches that may be incompatible with standard photoresist technology. For example, reactive ion etching (RIE) may require temperatures above 500.degree. C. that can damage the photoresist of the lithographic process as well as the titanate substrate.
Laser-based etching of a titanate substrate can damage the titanate substrate being etched. Laser-based etching of a titanate substrate also suffers from limited throughput as the area being etched is limited to the area of the substrate contacted by the laser. While etching a titanate material substrate by laser scribing generally results in less undercutting of the substrate, the laser radiation may damage the titanate substrate requiring repair by a high temperature (approximately 1,400.degree. C.) anneal. This anneal may produce undesirable oxidation states in the titanate substrate, reducing its desired electrical, optical, or mechanical properties. High temperature anneals, in addition, can cause changes and damage to other materials and structures present in a substrate.
Etching a titanate substrate by ion-milling can generate unacceptable defects in the titanate. These defects may include changes in a titanate's electrical, chemical, mechanical, optical, and/or magnetic properties.
Another anisotropic dry etching process previously developed includes using organic acid reagents to etch a titanate substrate. In order to obtain suitable etch rates, laser inducement of the etching is required. The difficult operation and maintenance of a laser limits the use of this process to small quantities.